1. Field of the Invention
The present invention relates to the design of position indicator displays for elevators. More particularly, the present invention relates to the circuitry used to drive a segmented display in the applications of an elevator position indicator.
2. Description of the Prior Art
Elevator position indicator displays are the displays that inform a person of the floor location of a particular elevator car at a particular moment in time. Elevator position indicator displays are commonly located in the lobby of buildings and within the actual cars of the elevator. The elevator position indicator display in the lobby of a building informs people in the lobby of the position and direction of the elevator car. In this manner they can gauge how long the wait will be before the elevator reaches the lobby. The elevator position indicator display within the elevator car informs a person of the floor level of the elevator so they know when to disembark the elevator car.
There are many different types of elevator position indicator displays, and there are no standards for their design. Additionally, different elevator systems operate at different supply voltages. Many elevator systems operate with twenty four volt power supplies. Other elevator systems are powered by one hundred and twenty volt power supplies. To further complicate matters, some elevator systems operate with alternating current, while others operate with direct current.
In addition to the wide range of power requirements used by various elevator systems, there is an equally large variety of position indicator displays in use. Although many of these position indicator displays use a segmented display to create alpha-numeric characters, the display drive circuits used to drive the segmented displays vary widely. The prior art of display diver circuits are exemplified by U.S. Pat. No. 5,644,326 to Lauzon, entitled, Display Device With Electrically Interconnected Display Elements; U.S. Pat. No. 5,703,607 to Tai, entitled Drive Circuit For Displaying Seven Segment Decimal Digit; U.S. Pat. No. 5,969,628 to Andre, entitled, Display Device For A 7-Segment Font; and U.S. Pat. No. 3,146,436 to Crow, entitled, Arabic Numeral Display Having Binary Code Conversion Matrix. Due to the complex designs of many display drive circuits, many displays are expensive to manufacture and complicated to repair.
Since elevators systems have different power requirements and vary in design, it is often difficult to repair or replace the elevator position indicator display used within that system. A need therefore exists in the art for a low cost versatile elevator position indicator display that can be retroactively added to most any elevator, regardless of the power specification used by that elevator. A need also exists for a simplified elevator position indicator display that uses a minimal amount of wiring and is easily maintained and repaired. These needs are met by the present invention as it is described and claimed below.
The present invention is a position indicator display system for an elevator. The elevator position indicator has a segmented display capable of producing alpha-numeric characters. The segmented display operates in a predetermined power range that may or may not match the operational voltage used by the rest of the elevator""s systems. Within the elevator position indicator, a display driver is coupled to the segmented display. The display driver receives a location signal from the systems controller of the elevator. The display driver arranges the location signal to drive the segmented display and produce an alpha-numeric character indicative of the location signal. Since the elevator""s operational voltage may differ from that of the elevator position indicator, a power conditioning circuit is provided. The power conditioning circuit selectively alters the power of the location signal so that the location signal falls within the operational power range of the segmented display.